GB1595013A

GB1595013A - Method of working coal seams

Info

Publication number: GB1595013A
Application number: GB7493/78A
Authority: GB
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1977-03-04
Filing date: 1978-02-24
Publication date: 1981-08-05
Also published as: BE864389A; US4304308A; DE2709437C2; US4301875A; DE2709437A1

Description

PATENT SPECIFICATION

( 11) 1 595 013 ( 21) Application No 7493/78 ( 22) Filed 24 Feb 1978 ( 19) ( 31) Convention Application No 2709437 ( 32) Filed 4 March 1977 in ( 33) Fed Rep of Germany (DE) ( 44) Complete Specification published 5 Aug 1981 ( 51) INT CL C 1 OB 57/20 ( 52) Index at acceptance CSE AA ( 54) METHOD OF WORKING COAL SEAMS ( 71) We, MESSERSCHMITT-BOLKOWBLOHM Gesellschaft mit beschrdnkter Haftung, of 8000 Mfinchen, German Federal Republic a Company organised and existing under the laws of the German Federal Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which iti 3 to be performed, to be particularly described

in and by the the following statement:-

This invention relates to a method of producing bores in coal seams using a high temperature working gas impinging on the coal at high pressure and high speed to comminute same Bores which extend in an oblique or horizontal direction are connected with vertical bores extending from the surface of the ground to the coal seam for the purpose of blowing in a gasification medium serving to gasify the coal below ground and with further vertical bores leading from the coal seam to the surface and through which the product gas resulting from the gasification of the coal is blown out.

In a coal seam to be worked by gasification of the coal below ground, connection channels are provided between the vertical bores mentioned In a method for providing connecting channels of this kind the coal is heated electrically between the vertical bores.

The provision of connecting channels in this manner involves considerable difficulties and expense and the risk of damage to the gastight covering layers The reason why damage to the said gastight covering layers is regarded as a disadvantage is that it results in uncontrollable escape of gasification medium and product gas Another factor is that if the two channel drifting methods are to be practicable the distances between the vertical bores to be interconnected must not exceed about 60 m If the latter method is used, therefore, the exploitation of a coal seam by gasification of the coal below ground necessitates a relatively closemeshed grid of vertical bores and this entails considerable costs.

The latter disadvantage also applies if recourse is had to a rotary boring process in order to produce, in the coal seam to be gasified below ground, an oblique or horizontal connecting bore between a vertical bore for blowing in a gasification medium and a vertical bore for blowing out the gas produced in the coal gasification The boring 55 apparatus used for this purpose, such as a boring head and a turbine drive, is a comparatively heavy structure and the weight and resulting immobility make it particularly difficult to control the equipment This is why 60 the maximum lengths of the connecting bores made with the boring apparatus in question are without exception limited to approximately 50 m Considerable cost is also incurred in such cases in order to provide 65 the fluid turbine with medium from the surface of the ground and to convey the drillings to the surface.

A system for raising the drilling material to the surface is also required in another 70 known process for the production of horizontal bores using a hot gas jet at high pressure and high speed from a source which is orientated and guided in the direction, of the boring axis and which is also held in a 75 suspended position opposite the wall of the boring.

This invention seeks to provide a method of working coal seams which will be an improvement on those known for the pro 80 duction of bores in coal seams, especially bores which take an oblique or horizontal course and by which vertical bores leading from the surface of the ground to the coal seam, for blowing in a gasification medium 85 serving to gasify the coal below ground, are connected with further vertical bores leading from the coal seam to the surface and serving to blow out the product gas resulting from the gasification of the coal 90 According to this invention there is provided a method for producing bores in coal seams using a high temperature working gas impinging on the coal at high pressure and high speed to comminute same, especi 95 ally bores which extend in an oblique or horizontal direction to connect vertical bores leading from the surface of the ground to the coal seam and through which a gasification medium serving to gasify the coal below 100 ground may be passed, with further vertical bores leading from the coal seam to the m U:

1,595,013 surface and through which product gas resulting from the gasification of the coal may be passed, in which method the comminuted coal in the bores produced by the working gas is brought into contact in situ with a gasification medium at appropriate temperature and pressure to gasify the comminuted coal The gasification medium may be produced using a rocket combustion process.

The method of this invention makes it possible, in an economical manner and without the danger of uncontrolled damage to gastight covering layers, to provide coal seams with bores which are exactly defined in position and direction and of a length far beyond that usually achieved In this connection the method of the invention is not dependent on a supply of energy from the surface of the ground and the drillings occurring in the thermal boring process undergo, before being raised to the surface, a conversion into gas which greatly simplifies this operation There is therefore no difficulty, even in coal seams situated at a considerable depth, in the provision of the best possible network of connecting bores for the gasification between vertical bores which are much farther apart than hitherto For this purpose, for example, use is now made of a bore matrix in which the bores are 500 m or more apart In comparison with the bore distances of about 60 m this affords a saving of vertical bores and thus of the cost of exploitation of coal seams, particularly those extending over a wide area.

It is advisable for the comminuted coal in the bores produced by the gas to be gasified in situ by means of a gasification medium which is a gasification medium, e.g hydrogen, steam or mixture of hydrogen and steam If this is done the gas produced in the gasification process has the quality of natural gas The situation is quite different, however, if the gasification of the drillings is effected, as is also possible, by means of an oxidizing gasification medim, such as air In these cases the primary gases produced by the coal gasification process are CO and H 2 O The carbon monoxide gas however largely undergo further combustion from the oxidizing gasification medium and becomes CO 2.

The process is simplified if the gasification medium is produced at the actual place of gasification and does not have to be conveyed there from the surface of the ground One way of doing this is to inject water or the like, accompanying a self supporting (rocket) combustion process, into the hot working gas,, or to ensure that the selection of the propellant for the combustion process is from the start a kind which will enable the resulting gas to function both as a gasification medium and as a working gas.

Finally, an advantageous method which can be used is for the product gas from the gasification of drillings to be further used on the spot as a fuel for the production of the working gas, the operation of conveying it to the surface thus being eliminated.

Claims

WHAT WE CLAIM IS:-

1 A method for producing bores in coal 75 seams using a high temperature working gas impinging on the coal at high pressure and high speed to comminute same, wherein the comminuted coal in the bores produced by the working gas is brought into contact 80 in situ with a gasification medium at an appropriate temperature and pressure to gasify the comminuted coal.

2 A method according to Claim 1, wherein the bores produced comprise bores 85 which extend in an oblique or horizontal direction to connect vertical bores leading from the surface of the ground to the coal seam and through which a gasification medium serving to gasify the coal below 90 ground may be passed, and further vertical bores leading from the coal seam to the surface and through which product gas resulting from the gasification of the coal may be passed 95 3 A method according to Claim 1 or Claim 2, wherein the gasification medium brought into contact in situ with the comminuted coal in the bores produced by the working gas is a hydrating gasification 100 medium.

4 A method according to Claim 3, wherein the hydrating gasification medium is hydrogen, steam or a mixture of hydrogen and steam 105 A method according to any preceding claim, wherein the gasification medium brought into contact in situ with the comminuted coal in the bores produced by the working gas is a gasification medium pro 110 duced in the location where drillings are gasified.

6 A method according to any preceding claim, wherein the gasification medium brought into contact in situ with the com 115 minuted coal in the bores produced by the working gas is also used as the working gas for the comminution of coal.

7 A method according to Claim 5 or Claim 6, wherein the said gasification medium 120 is produced using a rocket combustion process.

1,595,013 8 A method according to any preceding claim, wherein product gas resulting from the gasification of drillings is used for the production of the working gas.

9 A method according to Claim 1 substantially as herein described.

KINGS PATENT AGENCY LIMITED, By J B KING, Director, Registered Patent Agent, 146 a Queen Victoria Street, London, EC 4 V SAT.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd -1981.

Published at The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.